npf and ephemeral interfaces (tun0)

[David Brownlee <abs%absd.org@localhost>]

I have a server which needs to run an npf map rule on its OpenVPN
interface (tun0).

I can create the rule fine, but when the system restarts tnpf rejects
the rulset because there is no tun0 interface. Am I missing something?
Is there a way around this?

I have a couple of other systems still using pf to avoid this kind of issue :/

Relevant rule lines:

$vpn_if = inet4(tun0)
map $vpn_if dynamic $foohost      port 22 <- $foohost port 24

Thanks